Process and apparatus for roasting ores and recovering the gases therefrom.



F. VON SGHLIPPBNBACH.

PROCESS AND APPARATUS FOR ROASTING ORES AND REGOVEEING THE GASES THEREFROM. APPLICATION FILED FEB-12, 1910.

1,069,191, Patented'Aug. 5, 1913.

4 SHEETS-SHEET 1.

W1 tness es.

. i iw' i ys F. VON SGHLIPPENBACH. PROCESS AND APPARATUS FOR ROASTING onns AND REGOVERING THE GASES THEREPROK.

API'LIOATIOH FILED H13. 12, 1910.

1,069, 1 91 Patented Aug. 5, 1913.

F/ 0 m a v v w w wa *3 7; an l f as w; 92 792 g 92 6. 3 3 W fivesses v. Br e n60)- I liar/ 636 P. VON SCHLIPPENBACH. PROCESS AND APPARATUS FOR ROASTING OBES AND BEGOVERING THE GASES THERE-FROM.

' ,urmcuxon mum IEB. 12, 191'0.-

1,069,191 V Patented Aug. 5, 1913 I 5%.}, 4 snnms-snnm 4.

ma y "n a I Witnasses f i Ill/enter UNITED. STATES I PAEENT. OFFICE.

r'l znrx von sonnrrrnmaon, sumac. Gufiwr.

rnocnssj aim nrrnnawus r03 Toall whom it ma concern:

Be it known that I, FELIX, VON SCHLIP- PENBACH, a. 'subject'of the .Einperorof Ger;

many, residing at Stolberg, Binsfeldhammer,

, tain new and useful for RoastingOres and Recovering the Gases 1 amount of the-material to be roasted is ex-- Rhineland, Germanyhave invented a cerrocess and Apparatus Therefrom, of which the following is a specification. f v

. here are known certain roasting and oxidizing processes in which a certain posed to an air current until completely roasted, after which the roasted material is removed from-the roasting place and' fresh l ore is introduced to be treated. In these processes the gases produced. during acertain time from the beginning of the operation are suiiiciently. rich in, sulfur dioxid to he availed .of for the, manufacture of sulfuric acid. This stage of the operation hav- 'ing passed, however, the percentage of sulnow tilting I which is" caused'to pass above said grate.

' which in eontradistincftion 'te'the pots-may,

'past said device, or upon a stationary fur dioxid in the roasting. gases decreases to such a degree as to render the gases unfit for the manufacture of sulfuric acid. During the lapse of time which is necessary for removing the treated matter from the roasting place arid for charging fresh'masterial, no roasting gases are developed at 'all. Thus, in these roasting processes, a current of gas is obtained which is intermittent and very varying as to its content of sulfur dioxid, and itsutilization for'the manufacture of sulfuric acid 'has .not been possiblehitherto.

In operating the above mentioned roasting processes, the best known of which is the Huntington-Heberlein process,- until made use 0 "one plant being inmost cases providedi withseveral of these pots.

' For marrying out said roastin processes, .certain devices have] been a opted recently, in which thein aterial to be roasted is charged through 'a-stationary. charging deviceto a grate which is caused to move underneath by means of a movable charging evice In vthese recently used roasting devices nons'rme onus, unnnnrnon.

I Specification. Intent. im licationfiled February 1:, 1910.- sm's'i 11 542,454. J

- acid.

(converters) were generally I rate.

micovnmuc rnnfcasns paratus, the roastin rogresse" s from the P gases with the highest percentage of sulfur di-oxidare produced, whereas therichness' of the 'gases in sulfur dioxid decreases gradually in proportion as the respective, grate section isnearing the point of discharge. 'With such mechanical roasting a8; parat-uses a continuous gas current can obtained, but this gas current consists ofa mixture of gases rich in. sulfur dioxid and of gases poorin'sulfur 'dioxid, the yield of. sulfur dioxid of this gas mixture thus be'. ing too low to be made use of for the manu-Q facture of sulfuric acid.

Pan ing-aims" called automatic mechanical magi? a y...

Now the object of the present invention it is not only'to secure an uninterrupted as part of the roasting gases which is too poor in sulfur dioxid to be. availed of for the.

-manufactureof sulfuric acid, or the sulfur dioxid percentage ofv which is so low that when mixed .with the gas rich in 'sulfur dioxid a. gas mixture would I be obtained quite unfit for'themanufacture of sulfuric The ciently rich in sulfur dioxid as to allow -of its utilizationfor the manufacture of sulfuric acid.

Witha viewltoattajin thisob ject the are.

'75 current, but also toseparate from it t at-.'

object of the invention isthus topr'oe sa vide an uninterrupted gas current 'sufli entinvention pmvides' special-'ol1ecting* places or chambers for the gases rich in sulfur 'dioxid (called hereafter j rich .gases;,)- on the onehand', and' for the gases of a, Rug

lie ,95

percentage of sulfur dioxid (hereafter ca poor gasesj.) on thetotherhand. From the diiierent places wherethe gases are developed (ca-lled-hereafterf roasting places 1) they are directed to these' oollecting chamhers 'arovision being -made ['ito always forwar to. one and the same collecting chant air uninterrupted of of c 7 feeding device, for nstance a;

equal quality 5. e. of rich or of poor gas. In order to obtain this uninterrupted current of gas of the same kind, each roasting place may be connected with each collecting chamber by means of a separate'conduit, each oiv these conduits being closed and opened by an appropriate device. Now, during the operation, according to the state of the roasting process at one given roasting place, care will be takento close either the conduit for the poor gases corresponding to this place and to open simultaneously the conduit for the rich gases, or vice versa. Thus, as soon as the roasting operation at a roasting place which has been previously in communication with the collecting chamher for rich gases, has reached the period during which poor gases willbe developed, the communication of this roasting place with the collecting,chamber for rich gases will have to be interrupted and that with the collecting chamber for poor gases opened. p In the above mentioned. mechanical roasting devices, owing to the peculiar nature of the operation taking place there- I I upon, there always'exists the condition, that .one group of the roasting places is con- 'tinuously developing rich gases, and the oth r'group poor ones. Upon the grate of these mechanical roasting devices there are constantly, on the one hand, sections upon I which rich gases are being formed, and on. g the other hand, sections at which poor gases are produced- For this reason the present invention is adaptable to such mechanical roasting devices without requiring any change in respect of the roasting operation.

The annexed drawing; represent devices -for carrying out the invention.

Figures 1 and 2 are a vertical section and .a plan-view respectively. of an arrangement suitable for carrylng out the invention in'a furnace with an annular rotary 1 .grateicharged through a sta ionary feeding device. Figs. 3 and 4 show, in section and in plan-View respectively, an arrangement for carrying out the invention'by means of a" furnace with an annular stationary grate charged through a feeding device movable above the grate. Figs. 5 and 6 show an arrangement adaptable to [a straightline furnace with a stationary grate charged 'from a' feeding device-which is moved'above it. Figs.v 7 and Sjshow another arrangement for-carrying the invention into effect, which can be applied 'to' furnaces with movable grate and stationary feeding device, as well. as to furnaces with stationary grate and movable feeding device:

In the device shownin Fig. ,1, a is the annular grate rotatable around a vertical axis by any suitable means,' forinstance by; means of t0othed.w hee1s;1b is a 'stationa hopp an opening at the bottom, the length of which corresponds to the width of the grate. When the grate is caused to rotate, 1t

moves underneath the opening of the hop per 72 whereby a layer of fresh material is spread upon the grate. of material is brought to ignition in any suitable way as by the ignition means I and a current of air is forced through the ignited mass, the grate with the ignited mass continuing its motion in the direction .of the arrow. In the beginning, roasting gases are produced which are rich in sulfur This fresh layer dioxid. During '-the progression of the grate, the ore is more and more .d'esulfurized, and by the time the section of the grate previously charged underneath the hopper b with fresh material has reached acertain line for example II--IIo'f the circular path of the grate, the desulfuration of the material under; treatment upon the respective grate section has advanced to such a degree, that at the subsequent treatment the roasting gases PIOdJlCQd will be too low in sulfur dioXid tobe utilized for the manufacture of sulfuric acid. This condition of the material under treatment will be maintained during the advance motion of'the respective grate section say from the two collecting chambers, the following ar- 1 rangement has been provided: The inclosed space underneath the grate a is divided,

into several compartments 6 .the number of which may vary. From each of these compartments 6 two conduits f and 9 lead on,-

the delivery ends of which open. into the bottom parts 9' and 7cof two separate cham-.

hers h and 1' serving as collectors for the gases. The chamber 72. is formed by means of an annular bell Z, the chamber j by means of a cylinder-shaped bell m. From each of these bells branch off conduits n and 0 which deliver the. gases to an' y'desired'v spot, for

instance to the chambers for the manufac-. V ture of .sulfuricacid, or to the stack. The

bells Z and m are immersed in annular tanks and g filled with water, sand, glycerin or the like, with aview to sealing the chainbars iii. and against the outer air: 7

To the inner walls of each of the bells, and nicely above the bottoms j-and 76, upon the 100" Thus between the lines I-I and 110 as is well known, by means of partitions d a plates cover endipf the conduits f'and g, there are fastened clos1n pieces,- for instance plates and 8, the imensions of which are such 'fltt0 always cover a certain number of the j; -openingsof'the gas conduits f and g while j the c'penm of all-the other conduits f and jg are-left .ee. The bottoms y and 7c .of the -eo 1-lect1ng chambersh'and i are connected mth the tanks p and g and are supported theconduits-fand g. When the grate a the fu nace is caused to rotate, the con-' xdiiits and "g rotate with them and hence the bottoms; andfk'with the tanks p and g' parncipate'in the-frotation.

plates 1- and s will be determined by the 'fiumber of the 'co lii art'me'rits 6 being between the lines 11- -1 and III- 111 and between the lines 1-11 and II-II 'respec- Inthe roe-sting. apparatus shown in the; drawing, the part of" he grate between the! lines I- I-'-III and II.is left'empty for enabling the grate to cool prior to its being fedwith fresh material through the feeding.

device; "In order to prevent any admission of: atmospheric air to the collecting chamf hers lthronghithisempty part ofthe grate,

' the gas conduits] an 9 must, for the time are between the lines III.I II and I -I be kept closed by the plates r and s.

To *thisen'd thelengthjof both plates r and 8 has been extended sufiiciently,"so that the w alsorth'e mouths of the as con du'ts and, which are bet-ween the lines Ij- -I. 'Byjmeans o ,the arrangement hereinbefore-described, the preeent 'invention may be fout in :the' followin manner: hostatedg before, the gases pr ucedbetween i" "the lines I and II--II are sufficiently rich to tie-availed of for the manufacture of.

. acid, whereas the gases arising be- ..f'tw'een the lines 11- 11. and III-III are too #5 poor wine made use of for the manufacture of -sulfuric acid; and are to be directed into thest'ack. yProvisio'n must therefore be made jto'firaw, ofi separately the ases developed between the lines I-I and 1-11 and the produced-between the lines IIII and II, and'this in such a way as to real-. jize uninterrupted currents of gas. Inthe' position shown in the drawing, all the compartments e which are just between the lines I'I and 11 11, are connected, bymeans of the'conduits' f,-"with the annular collecting chamber h, owing to the fact that them'ouths of the correspondingl'conduits f are left uncovered by the plate '4'," all the'other gas con- "'60 duitsf emptying into the collecting chamber "h are closed, their mouths being' covered by l the plate 7*. On the other hand all the compartments e which arebetween the lines II-{+11 and III-41H are in communication with the central collecting chamber 2'' as the.

The number 'ofthe openings closed by. the 7 mouths of the corresponding conduits g between these lines are left free by the plate 8;

whereas all the other compartments'e are closed to the central collecting'cha'mber 2', as the mouths of the corresponding conduits g are covered by the plate 8. Inthe position shown in'the drawing, the rich gases developed between the lines II and I'III will thus be directed into the outer collecting chamber h When'ce they may be drawn ofl to the place of subsequent treatment (for instance the sulfuric acid, chambers). The poor gases. developed between the lines II-II and III'III will flow into the cen' t'ral collecting chamber 71 whence they may be drawnoif to the stack or to any other place. \Vlien the grated with the compartments 6 and-conduits f, gis being rotated, the rotating motion will be imparted also to. the bottom parts j and k and'the tanks 32 and q,

against the collecting chamber it will be 9 opened to 'thesam'e reason of the fact that the'nio-ut-hs of the corresponding conduits f'will successively emerge from beneath the plate r, whereby communication is established between the corresponding compartments e and the collecting chamber 11-. On the other hand, during the rotation of the grate, the mouths of the. conduits g hitherto closed by chef-plate s will appear, one after theothenfrom beneath the plate 5, and the compartments 6 corresponding to .munication with the inner collecting chamber'i, Whereasthe mouths of the conduits g hitherto open to the collecting chamber 2 will beclosed by reason of their passing undern eath the plate s-whereby also the respective compartments 6 will be? closed to the collecting chamber. 2'. r

It will be seen froin the foregoing that during the rotation 'of the-gra'tethe compartments e which are b'etween the lines I-I and II II will'be constantly in communica tion with the outer collecting chamber 71, whereas the compartments 6 which are between the lines 'IIII and III- III will always be in communication with the collecting chamber 1'. .Thus in the collecting chamber it there willjbe an uninterrupted 1 current of therich gases developed between the-lines II and II-11, whereas an'uninterrupted currentof the poor gases eveloped between the linesII-Il and III- III will'flow into the collecting chamber I a To each of the two pipes nand. odirecti'ng while t-hebellsl and man-d the plates and s these mouths will thus be brought intolcom- I the gases :trom the collecting chambers h and z" to the place of their further treatment or to the stack, there is connected a suction device, (for instancea fan) sucking the air from the top of the charge across the latter and causing the roasting gases gathering'in the'compartmentse to flow through the con-- duits fand' 9 into the collecting chambers handd. r

Byproviding a separate suction device for each collecting chamber, the further ad vantage is-realize'd that'it is possible to control, in a different manner, the admission of air to the different 'parts of the grate producing either rich or poor, gas, thus it will be possible to supply the partof the grate producing poor gases with a greater quantity of air or With air under higher pressure than the part in which rich gases are produced, or vice versa.

In the device shown in Figs. 3 and 4 the annular grate-a is stationary, thefeeding device 5 being moved above the grate. In

iur dioxid in the roasting gases produced upon the grate sections nearest to the start ing point will gradually decrease, and. by the time the feeding device has reached a certain point of its path, the gasesarising from the grate sections nearest to the starting point will have such alow content of sulfur dioxid as to be of no avail for the manufacture of sulfuric acid. In the meantime how- .ever, other sections 6 of the grate will have received fresh material from the feeding vice b and it is in-these sections that rich ases are nowbeing produced.

Inorder to. recover in this kind of roasting device the rich gases separately- ,from the poor ones, an arrangement might be made use of analogous to that described above with-reference to the Figs. 1 and 2. No other modification would be required than to provide stationary bottoms y' and 7.2 of the collecting chambers h and i with stationary tanks p and 9 whereas the bells Z and m will rotate with the feeding device b To this end the pipes n and 0 con nected with the bells, are provided with annular receptacles t and, u filled with water, sand, 'glycerin'or the'like, in which the stationarv partsof the pipes n and 0 are im- .partments will be opened and closed at fixed Owing to the' fact that the rotarymotion.

of. the feeding device bwill beimparted t0 the bells l -and m, the plates 7: and Is fastened to the bellswill be moved above the mouths'pfthe"gas' conduits f 9 which are arranged upon-the'st'ationary bottoms 7' k of the collecting chambers and these months -w-ill be opened and'closed according .to the respective jr'iositionsv of the feeding device Z2 It is ev-identthatv inthis'. mannerthe same effect will be realized as in the device shown inFigs. land 2 anddescribed hereinbefore, ,e. an' uninterrupted current of rich gases will passinto the collecting cham ber h and an uninterruptedcurrent of poor gases into the collecting chambe'r 5 There will be .but one' 'difl'erence in the working .of

the process with either of the two arrange- ,ments, in that with the device of Figs. 1

and 2, the development'ofythe richgases on the one hand, and-of the poor gases-om the, other hand, will always'take; place 11 on thesanue part of the hearth circuit, and t we the sections of the grate-will be opened andclosed always at one fixed point, whereas in the device according to 'Figs. 3 and 4:, the

. position of theplaces at which the rich' gases and the poor ones are developed will change In. a progressive'manner throughout the operation so that in the latter case the comintervals of time.

Figs. 5 and 6 show the invention adapted to Li-furnace with i t -fi aljv straight-lmed- 1 grate above which the f din device is moved. this furiiace in substantially the same mannor as in the furnace of Figs. 3 and 4.

There is but one difference in that, in the furnace shown in Figs. 5 and 6', the feeding rectilinear path, has to be carried back' to its starting polntwlthout-supplying the grate with material. In order to adapt the invenwith rectitation of the bells Z? and mimaybe-eflected w for instance by providing the bells with awith a, rack w toothed wheel a engagin fixed to the carriage w, w lch supports the feeding device b Durggf'th t t ok without loadfof the f ing, device 11 and the carriage w,*t he bells Z and-m must of course remain stationary; to this end appropriate devices have toz'beprovidedi for disengaging the racks 'wfrom the toothed wheels 72. I

The closing and opening of'the mouths of the gas conduits f and g? in the collecting 130 160.1. The roasting operation goes on'm' ,io sdevlce after hav ng reachedth'etend of its 1 chambers 12 and i will thus be efi'ected in 1 the same way as in the device of Figs. 3 and 4, and hence in the furnace according. ,to

' ends of the two outermost gas'conduits upon the bottom .of the. collectingchambers is twice the distance between the mouths of the other gas conduits. This arrangement is necessary for the reason that the heated matter has to be discharged from the outermost sections of the grate, at which the stroke of the feeding hopper begins, before fresh material can be delivered by the feeding device. The discharge-of. this first grate section takes place however at the time during which the other extreme section of the grate at the end of the-path of the feeding hopper is producing rich gases and must thus be closed against the collecting chamber of poor gases. On the other hand the first section of the grate, while be ing discharged, must be closed against both of the collecting chambers. in order to pre-- vent any admission of atmospheric air to these chambers. It will be seen that the condition, to, on the one hand, shut the last section of the grate against one of the collecting chambers, the first section on the other hand against both collecting chambers at the beginning of the path of the feeding device, is brought about by doubling the distance between the mouths of the two outmost gas conduits.

The removal of the treated material from the g'rate of 'the rectilinearfurnace is effected in any suit-able way known to those skilled in the art.

It is evidentthat the devices described,

, tacles are made use of ascollecting chambers, and plates fastened to the bells as closing devices, might be replaced by any other devices answering the same purposes.

The bells immersed in the receptacles filled with water might be replaced any other devices permitting a reciprocal motion of the two parts of the collecting chambers. A suitable device for replacing the bell is shown by way of example in the Figs. 7 and 8. In this arrangement the closing plates are replaced by a box-like sliding piece 3 which covers a certain number or the conduit-mouths. To this sliding box g .is connected an exit-pipe a through which the gases may pass to the place of further treatment or to the stack. In order to 1113111: tain covered also the mouths of the gas con: duits corresponding to the empty part of the grate, a plate r 'is connected withthe sliding box which covers a number of conduit mouths corresponding to the empty part of the grate. Theslidingbox y with plate ticipate in its rotation in the same manner as the closing plates in thedevices described above. It will be seen that the. sliding box 1/ replaces one of the bells made use. of in connection with the devices'des'cribed above.

The gases coming from the conduit mouths' are'connected with the bell m and parbe drawn oif separately from the gases collected in the box y.

The device shown in Figs. 7 and 8 may of course be made use of in connection with a stationary grate as well as with a rotary grate. This device is likewise adaptable in the case of a straight line grate and with 001- letting chambers with a t-o-and-fro motion.

In the foregoing but two collecting cham bers are spoken of, and accordingly two kinds of gases to be drawn'ofi separately. There might of course be obtained also three or more different currents of gas by increas-' ing the number of the accordingly.

Having thus fully described the nature of my invention, I claim as new and desire to secure by Letters Patent: I

1. The process of recovering separately the richer gases and the poorer gases in roasting operations, which consists in feeding upon a roasting hearth a layer of ore to collecting chambers be roasted maintainin the bod of orestationary upon the roasting hearth during, the roasting operation, subdividingthe ore":-

body into a plurality of individual roasting sections each producing gases of different percentages of sulfur dioxid with respect to the other roasting sections and the composition of gases evolved at one and the same roasting sectionvarying in the course of the roasting operation, conveying the richer. and the poorer gas currents respectively-of'each roasting section to separate .collectingplaces and connecting the roasting sectionswith the gas collecting. places according tothe composition of the gas then produced at said roasting sections, in such manner that, each gas collecting place shall be furnished with an uninterrupted current of gas of substantially constant average quality; substantially as described.

2. Apparatus for recovering separately the richer and poorer gases-in a roasting "plant havingu )lurality ofroasting places at which, at diierent'stages. the roasting process, gases of different percentages of 25 I the roasting operation has progressed atthe sulfur di-oxid are produced, separate collecting receptacles for each of the different kinds of gases,conduits from each of the roast-7' ng places to each ofythe collecting receptaeles, and means. for opening and closing 'r' is conduits; in accordance with the the richer gases and for the poorer stage to which the roasting operation has progressed at the several roasting places, to obtain an uninterrupted flow of gases of the desired quality to each collecting receptacle; substantially as described.

3. Apparatus for recovering. separately the richer and poorer gases given off in the roasting of sulfur-bearing ores, by mechanicaleroasting apparatus comprising a roast-- ing hearth divided into a plurality of-roastingplaces, means for progressively removing the roasted material from, and supplying fresh material to be roasted to, the hearth, separate collecting receptacles for ases, respectively, conduits from each 0' the roasting places to each of; the receptacles, and means for opening and closing the con duits in accordance with thestage to which several roasting places, to obtain an uninterrupted flow of gases of the desired quality to-each collecting receptacle; substantially 'as described.

, 4. The combination with mechanical oreroasting apparatus having a roasting-hearth divided into a plurality of roasting places and means for progressively removing the roasted material from, and supplying fresh material to be roasted to, the hearth, of

,means for recovering separately the richer and poorer gases given off in-the roasting operation, com rising separate collecting receptacles for t e richer gases and for the poorer gases, respectively, conduits from each of the roasting places to each of the receptacles, and means for opening and clos ing the conduits in accordance with the stage to which the roasting operation has progressed at the several roasting places, to obtain an uninterrupted flow of gases of the desired quality to each collecting receptacle; substantially as described.

5. The combination with mechanical oreroasting apparatus having a charging-hopper and a roasting-hearth divided into a a plurality of roasting places, said hearth and hopper being relatively movable so that the material to be roasted may be progressively supplied to and removed from the hearth, of

means of recovering separately the richer and poorer gases given oft in the roasting operation, comprising separate collecting receptacles for the richer gases and for the poorer gases, respectlvely, each of said receptacles comprising a bell and a bottompart movable with respect to oneanother,

conduits from each of the roa sting places to f roasting apparatus having a charging-hoppeer and an annular roasting-hearth divided into a plurality of roasting places, said hearth and hopper being relatively movable so that the material to be roasted may be progressively supplied to and removed from the hearth, of means ofrecovering separately the richer and poorer gases given oflf in the roasting operation, comprising separate collecting receptacles for the richer gases and for the poorer gases, respectively, said collecting receptacles being concentrically arranged within the annular hearth,

each ofsaid receptacles comprising a bell I and a bottom-part movable with respect to one another, conduits from each of the roasting places to each of the receptacles, mechanical connections between the movable elements of the receptacles and the movable element of the roasting apparatus, and conduit-opening and closing means actuated by the relative movement of the receptacle parts, whereby the conduits are connected with the receptacles in accordance with the stage to which the roasting operation has v progressed at the several places to obtain an uninterrupted flow of gas of the desired quality to each collecting receptacle; substantially as described.

7. The combination with mechanical oreroasting apparatus having a charging hopper and a roasting hearth divided into a plurality of roasting places, said hearth and hopper being relatively movable so that the material to be roasted may be progressively supplied to and removed from the hearth, of means of recovering separately the richer and poorer gases given off in the roasting operation, comprising separate collecting receptacles for the richer gases and for the poorer gases, respectively, each of said receptaclescomprising a bell and a bottompart movable with respect to one another, conduits from each of the roasting places to one of the relatively movable parts of each of the receptacles, mechanical connections between the movable elements of the receptacles and the movable element of the roasting apparatus, and a conduit-closing plate carried by that element of each of. the re quality to each collecting receptacle; subs'tantially as described.

FELIX VON SCHLIPPENBACH. In the presence .of-

W. J. REUTERS, HENRY 'QUADFLIEG.

neptacles t0 Whichthe' conduits are not led, whereby the conduits are connected with the receptacles in accordance with the stage to which the roasting operation has pro- 5 gressed at the several places to obtain an uninterrupted flow of gas of the desired 

